Optimum Design of an 18-Pulse Phase Shifting Autotransformer Rectifier to Improve the Power Quality of Cascaded H-Bridge Motor Driver

Due to its simplicity, efficiency, and dependability, the multipulse rectifier is widely used in electrical systems. In the presented work, an optimum design of an 18-pulse rectifier is achieved by comparing the most used configurations on the market. The 18-phase shifting autotransformer (18-PSAT) rectifier is a cheaper alternative to conventional rectifiers to reduce system harmonics. After a thorough study of the market needs and available use, this paper discusses four different structures that provide harmonic levels according to IEEE 519 limitations. An innovative 18-PSAT is shown, studied, simulated, produced, and tested with low power loss rates. The Delta differential configuration primarily emphasises lowering the loss power rating for improved power quality. With its simple structure, easy assembly, and direct connection to diodes, the proposed Delta differential configuration provides higher power quality and can cancel harmonics. To determine which 18-PSAT rectifier unit has the best weight, size, and power quality, a comparison of the selected topologies is made. A comprehensive comparison of each topology has simulation results showing current, voltage, and total harmonic distortion (THD) using MATLAB Simulink. The simulation results show that the total harmonic distortion is under 2.9 % when adopting the suggested Delta differential configuration topology. Compared to other designs, the suggested 18-pulse layout reduces overall cost and footprint by a large margin. It is also demonstrated that the DC load power is about 85 % of the recommended rectifier rating

Design of Short Circuit Indicator for Medium Voltage Systems

A phenomenon known as a short circuit occurs when the input terminals of a power source come into direct electrical contact with one another, which results in a very high flow of current. This results in the production of a significant amount of heat, which poses a risk to the system itself and those located nearby. So, it is vital to identify a short circuit problem and rapidly respond to it once it is identified. When connected, the Short Circuit Indicator automatically detects a short circuit in a circuit to which it is attached. We were able to show the short circuit in our circuit board by inserting a piece of wire that has a resistance value that is very low, almost equal to zero, and which, as a result, created a short circuit at the source connection. Three single-phase currents imply high voltage power line short faults. Zero sequence currents imply grounding failure. Line patrollers may see or hear short circuits or grounding issues on 3kV-40.5kV power distribution networks, switchgear, cable branching units, etc. Answer "What is a short circuit?" to study them. It's how? What time? and why? Short-circuit prevention. Short circuit (fault current) studies must be done to ensure that electrical system equipment can tolerate short circuit energy. Grounding shipboard equipment is difficult. Grounding the power transformer's return to the chassis eliminates direct wiring. Power supply load connects to transformer return. Overcapacity may damage equipment and endanger lives. Short circuits triggered many fires. Short circuits safeguard structures

Simulation of Induction Motor Driving by Bridge Inverter at 120 degrees, 150 degrees, and 180 degrees Operation

This paper presents a comparison between methods 120 degrees, 150 degrees, and 180 degrees operating modes in the bridge inverter used for induction motor application. This comparison gives full information about control strategies of conduction modes applying to the induction motor. That will make the choice at which mode the inductive motor will give the highest performance, the most efficiency, and which one of those modes is more speed response of the whole system. This study includes the model response of induction motor drive by using MATLAB Simulink software. The simulation model checked the performance of the induction motor main characteristic like speeds, currents, and torque under steady-state and various dynamic conditions. The final results of this study showed the induction motor gave optimum results when it is the switch controlled with the 150-degree mode of operation

SARS-CoV-2 vaccination modelling for safe surgery to save lives: data from an international prospective cohort study

Background: Preoperative SARS-CoV-2 vaccination could support safer elective surgery. Vaccine numbers are limited so this study aimed to inform their prioritization by modelling. Methods: The primary outcome was the number needed to vaccinate (NNV) to prevent one COVID-19-related death in 1 year. NNVs were based on postoperative SARS-CoV-2 rates and mortality in an international cohort study (surgical patients), and community SARS-CoV-2 incidence and case fatality data (general population). NNV estimates were stratified by age (18-49, 50-69, 70 or more years) and type of surgery. Best- and worst-case scenarios were used to describe uncertainty. Results: NNVs were more favourable in surgical patients than the general population. The most favourable NNVs were in patients aged 70 years or more needing cancer surgery (351; best case 196, worst case 816) or non-cancer surgery (733; best case 407, worst case 1664). Both exceeded the NNV in the general population (1840; best case 1196, worst case 3066). NNVs for surgical patients remained favourable at a range of SARS-CoV-2 incidence rates in sensitivity analysis modelling. Globally, prioritizing preoperative vaccination of patients needing elective surgery ahead of the general population could prevent an additional 58 687 (best case 115 007, worst case 20 177) COVID-19-related deaths in 1 year. Conclusion: As global roll out of SARS-CoV-2 vaccination proceeds, patients needing elective surgery should be prioritized ahead of the general population